Compressor unloader



Dec. 9, 1941. w. A. STEWART COMPRESSOR UNLOADER 3 Sheets-Sheet 1 Filed Aug. 7, 1941 P E W n 5 m o A n m A 4m I I W. v DYD ,w 4 M #1 u E 1 M 0 I, o

9, 1941- w. A. STEWART 2,265,675

COMPRESSOR UNLOADER Filed Aug. 7, 1941 3 Sheeis-Sh'eet 2 N OR ATTORNEY I Dec.-9, 1941. w. A. STEWART 2,265,675"

- I I COMPRESSOR UNLOADER Filed Aug. 7, 1941 3 Sheets-Sheet 3 Fiq!) Warren Afitawar't INV NTOR ATTORNEY struction and "combination 2 in the cylinder -rocated in the usual manner of the compressorshaft and Patented Dec. 9, 1941 I .Warren A. Stewart, Worthington Pump Holyoke, Mass, assignor to and Machinery Corporation, Harrison, N. 1., a corporation of Delaware Application August 7, 1941, Serial No. 405,733 1 Claims. (01. 230-22) .This invention relates to compressors, and more particularly to compressor loading and unloading means. i

An object of this invention is to provide an unupon its condition after it has started, pressor has picked up speed, thereby minimizin the load upon the prime mover of the compressor during starting and stopping periods of operation.

Another object of the present invention is to provide a stop and start unloader for compressors which utilizes a combination of centrifugal and magnetic actions .for operating a valve to control the loading and unloading of the com- With these and other objects in view, as may appear from the accompanying specification, the invention consists of various of parts, which will be first described in connectionjvitkthe accompanying drawings, showing a compressor unloader of the preferred form embodying the invention, and the features forming the invention will be specifically pointed out in the claims.

In the drawings: I Figure l is a vertical section through an air or gas compressor showing the improved unloadin means associated therewith.

cs2 is an enlarged sectional view of the improvedunlo'a Figur 2.

Figure 4 is across-section on line 4-4 of gum 2.

Figure 5 is an elevation, partly in section, of a modification of the invention showing the unloader operated from the shaft of the motor employed in driving the compressor.

Referring more particularly to the drawings, an air or gas compressor of any approved type is illustrated at I, having the compression space thereof, from which the air or gas compressed passes into the discharge line or pipe 3. The piston l of the compressor-is recipfrom the crank 5 the latter is rotated by any uitable type of prime mover (not shown). Y

The dischargepipe 3 has a conduit ll connected thereto. Howe this conduit may be connected to the compression space 2 of the compressor, directly, instead of features of con- 2 thus movin will be held on through the discompresor.

charge outlet line 3, without departing from the spirit of the present invention.

The conduit [0 opens into a valve casing ll,- whieh has a valveseat 12 formed therein, against which a valve I3 is adapted to seat, for cutting off communication from the interior of the conduit In with atmosphere, through the ports M in the valve housing II.

A valve operating stem valve housing II, for moving the valve 13. The inner or lower end of the stem i5 projects into the hub housing 16 formed on the compressor I,

I5 extends into the and rests upon the perimeter of a cam member N. This cam member ll rotates upon a stub shaft it, formed on the housing It. The cam II has a sleeve l9 thereon upon which is mounted, for rotation with the cam, This electric magnet 20 may be of any suitable type and size, of a type which may be purchased upon the market. r

The stub shaft i8 is provided with a longitudinally extending bore 2|, in which is rotatably seated a pin or shaft 22. A cup member 23 is carried by the shaft 22, and is rotatable either with or independently of the magnet20, as will be hereinafter described. This cup member 23 is connected through its hub- 24 and a yieldable coupling 25 with the crank shaft 6 of the compressor, so that the cup 23 1 The inner surface of the cup 23 is spaced frommg means the perimeter of the magnet 20, as clearly shown Figure 3 is a cross-section onimlsdlf ginthe drawirTgar cup 23. The rotation of the magnetic member 23 with the cup 23 will in turn cause rotation of the cam II. The cam l1, as will be noted in Figure 3' of the drawings, has a perimeter concentric of its axis of rotation, so that as the cam rotates it'wiil push the stem l5, which rests thereon, outwardly,

the stop 26 formed onthe perimeter of thecam engages the-stem H5, at which time the valve i3 its seat, closing communication between the discharge line 3 of the compressor. and atmosphere and resulting in loading of the The contact of thestop 20 with the an electric magnet 20..

As the speed of rotation of the valve 13 towards its seat, until stem l arrestsv the rotation of the cam l1 and consequently of the magnet so that during the continued operation of the compressor the cup 23 will rotate independently of the magnet 20.

When the compressor stops operation the spring 21, which is connected to the cam II at its one end and to the housing It at its other, will reverse the rotation of the cam, allowing the stem ii to move inwardly or downwardly under its own weight, permitting the valve l3 to move of! its seat l4 and thus opening the discharge of the compressor, or the compression space of the nation with a compressor including anoperating shaft and a compression space, of a valve housing having a passage open to said compression space and to atmosphere to permit unloadpressor is not operating to unload the comprescompressor, to atmosphere by means of the oonduit l0, valve housing II and ports ll. This-action allows the compressor to be operated in an 15 unloaded condition upon the compressor being again started, until of course such time as the compressor reaches its proper compressing speed. when the before described cycle of operation of the unloader will again shut of! communication with atmosphere. v i

In the modified construction shown in Figure 5 of the drawings the compressor 30 is shown as driven by an electric motor 3| through the medium of a suitable power transmission means 32. While an electric motor 3 I is shown, it is to be understood that any suitable type of prime mover may be employed for driving the-compressor without departing from the spirit ofthe' present invention.

The motor 3| has a driving shaft 33 from which the compressor is driven, and in this modified form the magnetic unloading mechanism 35 is associated with the shaft 33 of the motor 3| and is driven thereby for controlling the loading and unloading of the compressor. The valve 'structure 38 is identical in construction withthe 'valve structure shown in Figures 1 to 4 inclusive, and in fact the entire unloader mechanism. 35 is idensor, a magnet,'a cam connected to said magnet for movement therewith for seating said valve and holding it in seated position, means yieldably connected to said compressor shaft for rotation therewith and cooperating with said magnet when the-shaft reaches a predetermined speed of rotation to set up magnetic pull sufllcient to rotate said magnet and cam for seating the valve and holding it seated, and a stop on said cam for arresting movement of the cam and magnet when the valve is fully seated. 3. In an unloader, for compressors, the combination with a compressor including an operating. shaft and compression space, of 'a valve housing having a passage open to said compression space and to atmosphere to permit unloading of the compressor, a valvein said housing seated to close said passage to atmosphere to load the compressor and unseated when the compressor is not operating to unload the compressor, a magnet, a cam connected to said magnet for. movement therewith for seating said valve and holding it'in seated position, meansyieldably connected to said compressor shaft'for rotation and holding it seated, a stop on said cam for arresting movement of the cam and magnet when the valve is fully seated, and a spring contical with the unloader mechanism shown in 40 nected to said cam to move it out of valve hold Figures 1 to 4 of the drawings, and operates in ing position upon stopping of the compressor.

the same manner. 4. In an unloader forv compressors, the combi-' The conduit 31, which corresponds to theconn tion with a compressor. inclu f n 93 34 duit l0, connects the valve housing with the lll h ll lt and a compressionspace of a valve" discharge line 39 of the. compressor 30- to open 4:, housing having a passage open to said compresthisi discharge line and the compression space of sion space and, to atmosphere to permit unloadthe compressor 30 to atmosphere .for unloading ing of the compressor, a valve in said housing the compressor. in the same manneras described seated to close said passage to atmosphere to in connection with Figures 1 to 4 inclusive of the load thecompressor andunseated when the com-' drawings. r a pressor is not operating to unload the compres-,

It will be understood that the invention is not sor, a pair of elements mounted for independent ff to blimited to the specific construction or aror unitary movement and operative to seat said valveand to hold it seated for loading the C611":

rangement of parts "shown, but that theymay be. widely modified within-the invention defined pressor, one of said elements beingscofnnected to d -net, said elements-coeacting when the compres nation with a compressor including anoperating sor reaches a predetermined speed of operation shaftand a compression space; of a valve hous-- Ri e p netic P ll sumcient to m ve hem in having a passage open to said compression in unison to seat said valve and load the com- ,space and to atmosphere topermit unloading of .pressor- I i I the compressor, a valve in said housing In an nl ade 1' 1 mpressors. the combito close said passage to atmosphere to load the i n i h a omp essor cluding an o era i compressor and unseated when the compressor shaft d pr si n pace, of a valve 110118- is not operating to unload thecompressor, a 05 8 having a P 88 Open .to said compression magnet, a cam connected to said magnet for a ace d o osp ere o pe mit oading of movement therewith for seating said' valvejand the pr ssor. a valve in said housing seated holding it in seated positionrmeans yieldably to close and W to a n n t vloodtho connected to said compressor shaft for rotation ompressor and seated hen t e-comm therewith and cooperating with said magnet is not operating to nload the compressor. apair when the shaft reaches a predetermined speed of 01 elements ed 1 12 5 rotation to set up magnetic pull sufiicient' to romovemgmt n Opera-five 0 4 i V 78 III! tate said magnet and cam for seating the valve 4 to hold it seated for loading the compressor, one and holding it'seated; 1 of said elements to 2. In an unloader for compressors,- the oombiformovement upon-operation or the 1. In an unloader for compressors, the combi one of said elements being a magnet, said elements co-acting when the compressor reaches a predetermined speed of operation to set upmagnetic pull sufiicient to move them in unison, and means operated upon unitary movement of said elements to seat said valve and load the compressor.

6. In an unloader for compressors, the combination with a compressor including an operating shaft, and a compression spacefof a valve housing having a passage open to said compression space and to atmosphere to permit unloading of the compressor, 'a valve in said housing seated to close said passage to atmosphere to load the compressor and unseated when the compressor is not operating to unload the compressor, a pair of elements mounted for independent or unitary movement and operative to seat said valve and to hold it seated for loading the compressor, one or said elements being connected to said shaft for movement upon operation of the compressor, one of said elements being a magnet, said elements co-acting when the compressor reaches a predetermined speed of operation to set up magnetic pull in unison, means operated upon unitary movement oi'said elements to seat said valve and load the compressor, and means connected to said valve seating means to move the valve seating means upon stopping of the compressor to permit unseating of the valve and unloading of the compressor.

'7. In combination, a compressor including a compression space, an operating motor for said compressor having an operating shaft, a valve housing carried by said motor and having a passage open to the compression space and to atmosphere to permit unloading of the compressor, a valve in said housing seated to close said passage to atmosphere to load the compressor, a

magnet, means actuatedby movement of said magnet to seat said valve to load the compressor. means movable by rotation of said -motor shaft and cooperating with said magnet to set up magnetic pull when the shaft reaches a predetermined speed of rotation to move the magnet for operating said valve seating means.

- WARREN A. STEWART.

suflicient to move them 

